Microbiology Lecture Exam #2

Metabolism

All chemical reactions in a cell, including building and breaking down.

Anabolism

Building larger molecules from smaller ones. Needs energy (ATP).

Catabolism

Breaking down larger molecules into smaller ones. Releases energy (ATP or heat).

ATP

The main energy currency of the cell. Powers processes like building molecules, transport, and movement. Made during catabolism, used during anabolism.

What are enzymes and their function

Metabolic pathways

Aerobic metabolism

• Needs oxygen.- Produces a lot of ATP.

Anaerobic metabolism

• Doesn't need oxygen.- Produces less ATP than aerobic metabolism.

Fermentation

Genetics

The study of how traits are inherited and vary.

Genome

All the genetic material in an organism.

Chromosome

A packaged DNA molecule inside a cell.

Gene

A section of DNA that codes for a protein or RNA.

Genetic Code

Rules for how genetic information is turned into proteins.

Vertical Gene Transfer

Genetic material passed from parent to offspring.

Levels of Genetics

Key terms in genetics: genome, chromosome, gene, DNA, genotype, phenotype, allele, homozygous, heterozygous.

Gene Expression

Using gene information to make a product, like a protein.

DNA

Double-stranded, has deoxyribose sugar and thymine (T).

RNA

Single-stranded, has ribose sugar and uracil (U) instead of thymine.

What is the structure of DNA

• Made of nucleotides (phosphate, sugar, base).- Bases pair: A-T, G-C.- Strands run in opposite directions (antiparallel).

What are the DNA replication steps?

initiation (where the double helix unwinds), elongation (where new strands are created using DNA polymerase), termination (where the process is completed).

Initiation

Helicase unwinds DNA.

Elongation

DNA polymerase adds new bases.

Termination

Ligase seals DNA pieces.

Antiparallel Effect

DNA strands run opposite ways. One strand builds continuously, the other in small pieces (Okazaki fragments).

Okazaki fragments

Short DNA pieces made on the lagging strand.

5' and 3'

Directions of DNA strands. DNA polymerase adds bases from 5' to 3'.

Replication fork

Where DNA unwinds and copies itself.

What does helicase do

Unzips DNA.

DNA Polymerase III

Adds bases and checks for errors.

DNA Polymerase I

Removes starter pieces (primers) and fixes DNA.

What does ligase do

Connects DNA fragments.

What does primase do

Makes RNA starter pieces (primers).

What is semi conservative replication?

New DNA has one old strand and one new strand.

What is central dogma?

How genetic info flows: DNA to RNA to Protein.

If every protein encodes for a trait

Each gene makes a protein, which controls a trait.

What is a codon

Three mRNA bases that code for one amino acid.

What is the role of RNA in gene expression

RNA helps make proteins: mRNA carries code, tRNA brings amino acids, rRNA forms ribosomes.

What structures part of translation apparatus in protein synthesis

mRNA, tRNA, rRNA, ribosomes, and enzymes.

mRNA

Carries DNA's genetic code.

tRNA

Brings amino acids to the ribosome; has an anticodon.

What are the different types of mutations

Types are insertion (add), deletion (remove), substitution (change).

Insertion mutation

Adds a base.

Deletion mutation

Removes a base.

substitution mutation

Replaces one base with another.

What is the link between mutations and gene expression in terms of protein synthesis

Mutations change DNA, which can change the mRNA and the protein it makes, affecting its structure or function.

frameshift mutation

Changes how the gene is read (due to insertion/deletion).

nonsense mutation

Creates an early stop signal.

missense mutation

Changes one amino acid.

Silent mutations

No change to the amino acid.

How does a mutation impact the structure, function, and formation of proteins

Mutations can change a protein's shape and job, possibly causing it to lose function or gain new traits.

What is a recombinant organism?

An organism with genes from a different organism.

What is the definition and benefit to the organism

Benefit: Makes the organism more genetically diverse and adaptable.

Vertical gene transfer

From parent to offspring; doesn't add diversity.

transformation gene transfer

Taking in free DNA from the environment.

transduction gene transfer

DNA transfer by a virus (bacteriophage).

conjugation gene transfer

Direct DNA transfer between bacteria using a pilus.

Plasmids

Small, circular DNA that copies itself separately from the main chromosome.

What links plasmids and pathogenicity

• Plasmids carry genes for antibiotic resistance, toxins, and virulence.- Help bacteria survive and share DNA (e.g., via conjugation).

How are chromosome enhancing pathogenicity, benefits the bacteria? bad for humans?

Benefits bacteria by: improving resistance, aiding adaptation, and assisting infection. Bad for humans by: causing drug resistance and increasing virulence.

Define nutrients and its importance to bacterial growth

Nutrients are substances bacteria need from their environment for energy, building cells, and carrying out life processes.

Saprobes

Free-living microbes that eat dead organic matter, breaking it down with enzymes and absorbing nutrients.

parasites

Live on or in a host, causing harm (also called pathogens).

Decomposers

Saprobes (like fungi/bacteria) that break down dead organisms and recycle nutrients.

What are characteristics of plasma membranes

• Selectively permeable (lets some things in/out).- Controls what enters and exits the cell.- Works with the cell wall.

Osmosis

Movement of water across a membrane from low solute to high solute concentration.

What are the physical and chemical factors that impact bacterial growth

• Physical: Temperature, pH, water pressure, radiation, gases, other microbes.- Chemical: Nutrients, oxygen, toxins.

Minimum temperature

Lowest temperature for growth.

Maximum temperature

Highest temperature before proteins break down.

Optimum temperature

Best temperature for fastest growth and cell activity.

Psychrophiles grow in what temperature

Grow below 15^\circ C (cold-loving).

Mesophiles grow in what temperature

Grow best at 20-40^\circ C (like most human pathogens).

Thermophiles grow in what temperature

Grow above 45^\circ C (heat-loving).

Enzymes and proteins grow in what temperature

High temperatures can destroy them, stopping cell activity and killing the cell.

What is denaturation

When proteins lose their shape and stop working due to heat or pH changes.

Acidic

pH < 7.

Neutral

pH = 7.

Basic (alkaline)

pH > 7.

What is the impact of high or low pH levels on bacterial growth

Extreme pH can destroy enzymes and harm cells, stopping growth.

obligate acidophiles

Need acidic environments to grow (like some molds and yeasts).

Isotonic

Equal solute in/out → water moves equally.

Hypotonic

Less solute outside → water enters cell → cell may burst.

Hypertonic

More solute outside → water leaves cell → cell shrinks (plasmolysis).

What is plasmolysis?

Cell membrane pulls away from cell wall due to water loss, stopping growth.

Specifically, how high concentrations of sugar and salt limit bacterial growth?

High sugar/salt creates a hypertonic environment, pulling water from cells and stopping growth (used in food preservation).

What is the impact of other organisms on bacterial growth and what Influences the growth

Microbes interact (compete, cooperate, inhibit), which can help or hurt their growth.

How are microbes in biofilms suited compared to \"free living microbes\"

Biofilms are microbe communities on surfaces, protected by a matrix. They are more resistant to antibiotics and harsh conditions than free-living microbes.

Three categories of microbes

Aerobes (need oxygen), anaerobes (no oxygen), facultative aerobes (with/without oxygen).

Aerobes

Need oxygen to grow.

Anaerobes

Cannot live with oxygen.

Facultative anaerobes

Can grow with or without oxygen (more at the top with oxygen).

How can oxygen be beneficial and/or harmful to microbes?

• Beneficial: Used for metabolism (aerobic respiration).- Harmful: Can create toxic byproducts unless neutralized by enzymes.

Obligate aerobes

Grow only where oxygen is highest (top of tube).

Obligate anaerobes

Grow only where there's no oxygen (bottom of tube).

Microaerophiles

Grow just below the surface (need a little oxygen).

Aerotolerant anaerobes

Grow evenly; don't use oxygen, but aren't harmed by it.

What are the four stages of bacterial growth

Lag, Log (Exponential), Stationary, Death phases.

Lag Phase

Cells adjust, no division yet.

Log (Exponential) Phase

Rapid cell division and growth.

Stationary Phase

Growth slows; nutrients run out, waste builds up.